The invention relates to the field of solar energy, in particular to a method for purifying industrial silicon by means of Al-Zr alloy. The method comprises the steps that three alloy elements including industrial silicon, aluminum granules and zirconium columns are mixed and contained in a crucible according to a certain proportion, the crucible is placed in a quartz tube, the quartz tube is subjected to vacuum sealing and then put into a box-type furnace to be smelted by increasing the temperature to 900-1,100 DEG C, heat preservation is conducted for 2-3 h, furnace cooling is conducted at different cooling speeds till the temperature is lowered to 580-600 DEG C, and finally air cooling is conducted. According to the method, by adding a small quantity of Zr element, on one hand, an impurity B is dissolved into a compound Si2Zr prepared from Si and Zr, and then the impurity B can be conveniently removed; on the other hand, the dendritic crystal width of primary silicon and the occupation proportion of the primary silicon in the structure can be effectively increased. The method has the advantages that the cycle is short, energy consumption and pollution are low, the technology is stable, and the B element in the industrial silicon can be quickly and massively removed.